The present invention relates generally to heat-transfer label assemblies and more particularly to a novel heat-transfer label assembly.
Heat-transfer labels are implements commonly used to decorate and/or to label commercial articles, such as, and without limitation to, containers for beverages (including alcoholic beverages, such as beer), essential oils, detergents, adverse chemicals, as well as health and beauty aids. As can readily be appreciated, heat-transfer labels are desirably resistant to abrasion and chemical effects in order to avoid a loss of label information and desirably possess good adhesion to the articles to which they are affixed. Heat-transfer labels are typically constructed as part of a heat-transfer label assembly, with one or more heat-transfer labels printed on a removable carrier web.
One of the earliest types of heat-transfer label assemblies is described in U.S. Pat. No. 3,616,015, inventor Kingston, which issued October, 1971, and which is incorporated herein by reference. In the aforementioned patent, there is disclosed a heat-transfer label assembly comprising a paper sheet or web, a wax release layer affixed to the paper sheet, and an ink design layer printed on the wax release layer. In the heat-transfer labelling process, the label-carrying web is subjected to heat, and the label is pressed onto an article with the ink design layer making direct contact with the article. As the paper sheet is subjected to heat, the wax layer begins to melt. This enables the paper sheet to be released from the ink design layer, with a portion of the wax layer being transferred with the ink design layer onto the article and with a portion of the wax layer remaining with the paper sheet. After transfer of the design to the article, the paper sheet is immediately removed, leaving the design firmly affixed to the article and the wax transferred therewith exposed to the environment. The wax layer is thus intended to serve two purposes: (1) to provide release of the ink design from the web upon application of heat to the web and (2) to form a protective layer over the transferred ink design. After transfer of the label to the article, the transferred wax release layer is typically subjected to a post-flaming or post-heating technique which enhances the optical clarity of the wax protective layer (thereby enabling the ink design layer therebeneath to be better observed) and which enhances the protective properties of the transferred wax release.
Many heat-transfer label assemblies include, in addition to the layers described above, an adhesive layer (comprising, for example, a polyamide, phenoxy, or polyester adhesive) deposited over the ink design to facilitate adhesion of the label onto a receiving article. An example of a heat-transfer label assembly having an adhesive layer is disclosed in U.S. Pat. No. 4,548,857, inventor Galante, which issued Oct. 22, 1985, and which is incorporated herein by reference. Additionally, many heat-transfer label assemblies additionally include a protective lacquer layer interposed between the wax release layer and the ink layer. An example of such a label assembly is disclosed in U.S. Pat. No. 4,426,422, inventor Daniels, which issued Jan. 17, 1984, and which is incorporated herein by reference.
One phenomenon that has been noted with heat-transfer label assemblies of the type described above containing a wax release layer is that, quite often, a degree of hazing or a xe2x80x9chaloxe2x80x9d is noticeable over the transferred label when the transfer is made onto clear materials. This xe2x80x9chaloxe2x80x9d effect, which persists despite post-flaming or post-heating and which may detract from the appearance of the label, is caused by the presence of the wax coating around the outer borders of the transferred ink design layer. Hazing due to the wax release layer may also appear in xe2x80x9copen-copyxe2x80x9d areas of the label, i.e., areas of the label where no ink and no protective or adhesive lacquers are present, and also may detract from the appearance of the label.
In addition to and related to the aforementioned problem of hazing, when heat-transfer labels of the type described above are applied to dark-colored containers, the outer wax layer of the label often appears as a whitish coating on the container, which effect is undesirable in many instances. Furthermore, scratches and similar abrasions to the outer wax layer of the label can occur easily and are readily detectable.
Accordingly, to address the aforementioned issues, considerable effort has been expended in replacing or obviating the need for a wax release layer. One such approach to this problem is disclosed in U.S. Pat. No. 4,935,300, inventors Parker et al., which issued Jun. 19, 1990, and which is incorporated herein by reference. In the aforementioned Parker patent, the label assembly, which is said to be particularly well-suited for use on high density polyethylene, polypropylene, polystyrene, polyvinylchloride and polyethylene terephthalate surfaces or containers, comprises a paper carrier web which is overcoated with a layer of thermoplastic polyethylene. A protective lacquer layer comprising a polyester resin and a relatively small amount of a nondrying oil is printed onto the polyethylene layer. An ink design layer comprising a resinous binder base selected from the group consisting of polyvinylchloride, acrylics, polyamides and nitrocellulose is then printed onto the protective lacquer layer. A heat-activatable adhesive layer comprising a thermoplastic polyamide adhesive is then printed onto the ink design layer.
Although the above-described Parker label assembly substantially reduces the wax-related effects discussed previously, said label assembly does not quite possess the same release characteristics of heat-transfer label assemblies containing a wax release layer. In fact, when put to commercial use, the polyethylene release layer of the Parker label assembly was found to become adhesive when subjected to the types of elevated temperatures typically encountered during label transfer. Accordingly, another type of heat-transfer label assembly differs from the Parker heat-transfer label assembly in that a very thin layer or xe2x80x9cskim coatxe2x80x9d of carnauba wax is interposed between the polyethylene release layer and the protective lacquer layer to improve the release of the protective lacquer from the polyethylene-coated carrier web. The thickness of the skim coat corresponds to approximately 0.1-0.4 lbs. of the wax spread onto about 3000 square feet of the polyethylene release layer. The aforementioned xe2x80x9cskim coat-containingxe2x80x9d heat-transfer label assembly also differs from the Parker label assembly in that the heat-activatable adhesive of the xe2x80x9cskim coatxe2x80x9d label assembly is printed over the entirety of the ink and protective lacquer layers, with the peripheral edges of the adhesive layer in direct contact with the wax skim coat.
In addition to improving the release characteristics of the label assembly, the aforementioned wax skim coat also enables the label to be stretched non-uniformly, if desired, for application to articles of tapered cross-section.
An example of a xe2x80x9cskim coat-containingxe2x80x9d heat-transfer label assembly of the type described above is disclosed in U.S. Pat. No. 5,800,656, inventors Geurtsen et al., which issued Sep. 1, 1998, and which is incorporated herein by reference. According to one embodiment, the aforementioned Geurtsen label assembly is designed for use with silane-treated glass containers of the type that are subjected to pasteurization conditions, the label assembly including a support portion, a skim coat positioned on top of the support portion and a transfer portion positioned on top of the support portion. The support portion includes a sheet of paper overcoated with a release layer of polyethylene. The transfer portion includes an organic solvent-soluble phenoxy resin protective lacquer layer, an organic solvent-soluble polyester resin ink layer over the protective lacquer layer, and a water-dispersible acrylic adhesive resin layer over the ink and protective lacquer layers and onto a surrounding portion of the skim coat.
Examples of other xe2x80x9cskim coat-containingxe2x80x9d heat-transfer label assemblies are disclosed in the following U.S. patents, all of which are incorporated herein by reference: U.S. Pat. No. 6,096,408, inventors Laprade et al., issued Aug. 1, 2000; U.S. Pat. No. 6,033,763, inventors Laprade et al., issued Mar. 7, 2000; U.S. Pat. No. 6,083,620, inventors Laprade et al., issued Jul. 4, 2000; and U.S. Pat. No. 6,099,944, inventors Laprade et al., issued Aug. 8, 2000.
Although the release properties of heat-transfer label assemblies that include the aforementioned wax skim coat are much improved compared to similar heat-transfer label assemblies lacking said wax skim coat, said label assemblies do result in a portion of the wax skim coat being transferred to the article being decorated during label transfer. As a result, particularly when the labelled article is dark in color, a wax residue is often visible to the naked eye on the article around the peripheries of the label. Such a wax residue or margin, for the reasons discussed above, is undesirable from an aesthetic standpoint. In addition, said wax residue precludes the possibility of decorating articles, such as containers, with xe2x80x9cwrap-aroundxe2x80x9d labels of the type that completely encircle an object since the adhesive present at the trailing end of the label will not adhere to that portion of the article covered by the wax residue that is deposited with the leading end of the label.
It is an object of the present invention to provide a novel heat-transfer label assembly.
It is another object of the present invention to provide a heat-transfer label assembly as described above that overcomes at least some of the problems associated with existing heat-transfer label assemblies of the type described above.
In furtherance of the above and other objects to be set forth or to become apparent from the description to follow, and according to one aspect of the invention, there is provided a heat-transfer label assembly, said heat-transfer label assembly comprising:
(a) a carrier;
(b) a heat-transfer label, said heat-transfer label being positioned over said carrier for transfer of said heat-transfer label from said carrier to an article under conditions of heat and pressure, said carrier extending beyond the periphery of said heat-transfer label to yield one or more exposed areas of said carrier, said heat-transfer label comprising
(i) an ink design layer, and
(ii) a heat-activatable adhesive layer over said ink design; and
(c) a mask positioned over at least a portion of said one or more exposed areas of said carrier and not positioned over said heat-transfer label, said mask adhering to said carrier during heat-transfer of said heat-transfer label.
In a first preferred embodiment, the carrier is a paper substrate overcoated with a layer of polyethylene, and a skim coat of wax overcoats the polyethylene layer. One or more heat-transfer labels are printed onto the skim coat and are spaced apart from one another, each heat-transfer label comprising a protective lacquer layer printed onto the slim coat, an ink design printed onto the protective lacquer layer, and a heat-activatable adhesive layer printed over the ink design, any exposed areas of the protective lacquer layer and a surrounding area of the skim coat. The periphery of the skim coat extends beyond the peripheries of the labels and is, therefore, uncovered by the labels. The mask is deposited over all of the areas of the skim coat that are left uncovered by the labels and serves to prevent a wax border from being transferred onto the decorated article around the periphery of the transferred label.
A second preferred embodiment differs from the first preferred embodiment in that the mask is not only applied to all of the areas of the skim coat that are left uncovered by the labels but is also applied to all areas of the heat-activatable adhesive layers, except for those areas of the adhesive layers positioned directly over the ink designs. As a result, those portions of the protective lacquer layers and adhesive layers that extend beyond the peripheries of the ink designs become fixed to the carrier by the mask and are not transferred during label transfer, thereby leaving only the ink designs, those portions of the protective lacquer layers positioned directly below the ink designs and those portions of the adhesive layers positioned directly above the ink designs to constitute the heat-transfer labels.
A third preferred embodiment differs from the first preferred embodiment in that the mask is only applied to areas of the skim coat that are disposed proximate to the leading end of the label. Although this embodiment does not completely eliminate the aesthetic issues associated with a wax margin (particularly along the top and bottom edges of the label), it does permit the label to be used as a xe2x80x9cwrap-aroundxe2x80x9d label.
A fourth preferred embodiment differs from the first preferred embodiment in that the assembly does not include a wax skim coat and in that the carrier comprises a polymeric substrate and a release coating, said release coating being deposited on top of the polymeric substrate. The polymeric substrate is preferably a clear polymeric film selected from the group consisting of polyesters, such as polyethylene terephthalate, polyethylene napthylene; polyolefins, such as polyethylene and polypropylene; and polyamides. The coating, which is preferably clear, is applied directly on top of the substrate and is a non-wax, non-silicone, thermoset release material that separates cleanly from the label and is not transferred, to any visually discernible degree, with the label onto an article being labeled. The coating preferably has a thickness of about 0.01 to 10 microns, more preferably about 0.02 to 1 micron, even more preferably about 0.1 micron. In addition, the coating preferably has a total surface energy of about 25 to 35 mN/m (preferably about 30 mN/m), of which about 0.1 to 4 mN/m (preferably about 1.3 mN/m) is polar surface energy. Furthermore, when analyzed by XPS (X-ray photoelectron spectroscopy), the coating preferably has a carbon content (by atomic %) of about 90 to 99.9% (preferably about 97%) and an oxygen content (by atomic %) of about 0.1 to 10% (preferably about 3%).
A fifth preferred embodiment differs from the first preferred embodiment in that the protective lacquer layer is printed over substantially the entirety of the skim coat, in that the adhesive layer is printed over the ink designs and substantially the entirety of the protective lacquer layer, and in that the mask is printed over substantially the entirety of the adhesive layer, except where the adhesive layer is positioned directly over the ink designs.
For purposes of the present specification and claims, it is to be understood that certain terms used herein, such as xe2x80x9conxe2x80x9d or xe2x80x9cover,xe2x80x9d when used to denote the relative positions of two or more layers of a heat-transfer label, are primarily used to denote such relative positions in the context of how those layers are situated prior to transfer of the transfer portion of the label to an article since, after transfer, the arrangement of layers is inverted as those layers which were furthest removed from the associated support sheet are now closest to the labelled article.
Additional objects, as well as features, advantages and aspects of the present invention, will be set forth in part in the description which follows, and in part will be obvious from the description or may be learned by practice of the invention. In the description, reference is made to the accompanying drawings which form a part thereof and in which is shown by way of illustration specific embodiments for practicing the invention. These embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is best defined by the appended claims.